Primary functions of storm water conveyance systems include the prevention of erosion and flooding by channeling surface water runoffs into networks of underground pipes and/or open channels for controlled distribution. Surface water runoffs taken into storm water conveyance systems can be directed to water treatment facilities and/or open bodies of water, such as rivers, lakes, and oceans. Storm drains represent the intake point of surface water runoffs into the storm water conveyance system.
Surface water runoff enters a storm drain through an opening called a storm drain inlet. Typically, the storm drain inlet allows water to run into a catch basin. And the catch basins has an intake opening and an outlet pipe that provides a path for water to run from the catch basin into the remainder of the storm water conveyance system.
Debris removal is an important function of storm drain filtration systems because debris entering storm drains along with surface water runoff may clog storm drains, resulting in flooding, or run through storm drains, resulting in damage to water treatment facilities and/or pollution of receiving water bodies. Storm drains can incorporate a variety of filter systems designed to reduce the amount of debris that enters the storm drain and/or the storm water conveyance system. Examples of such filtering systems include storm drain inlet screens, catch basin filters, pre-treatment filters, and connector pipe screens.
While storm drain filtration systems should inhibit debris and trash from entering into the storm drain and/or storm water conveyance system, they should not interfere with the primary functions of the conveyance system, which is the prevention of erosion and flooding. One strategy for achieving these objectives are storm drain filtration systems comprising screens that occupy a closed position under dry conditions, or conditions of low or moderate water flow, and an open position under conditions of moderate to heavy water flow. In such systems, screens in the closed position impede the passage of debris while permitting low to moderate water flow; and screens in the open position allow the passage of debris and water such that the screens themselves do not plug the storm drains and cause flooding.
In the context of curb inlet filtration units, debris detained by such screens when there is no, low, or moderate water flow can be removed by a street sweeper, keeping the removed debris out the storm drain and the storm water conveyance system. In the context of connector pipe filtration units, debris detained by such screens when there is low to moderate water flow can be removed from the catch basin of the storm drain by maintenance crews, keeping the removed debris out of the remainder of the storm drain and/or storm water conveyance system.
A curb inlet filtration unit installed in a curbside drain opening which detains debris at no or low flow rates, but which opens when the rate of water flow is sufficiently high, is described in Jarvis U.S. Pat. No. 8,277,645. An inherent problem with known devices such as in the Jarvis patent is that the screen has an open configuration bias, such that the described curb inlet filtration unit has a high failure rate.